It was an ordinary day's fishing for a man until he pulled out a huge 'monster'

Ma Hongjun and his two other fellow fishermen were surprised after catching a large kaluga sturgeon weighing 513 kilos.

The three fishermen from north China reeled in the massive fish from Amur River on May 19, 2018, as reported by Daily Mail.

It was believed to be the heaviest freshwater sturgeon caught in the region of Tonjiang and Fuyuan in the last decade. Measuring 3.59 meters long, it was also believed to be over 100 years old.

The fish, which stirred up interest in the community, went into the hands of a local fishery release station, which bought it for over $33,000.

Ma, 53, and his fellow fishermen dragged the fish to shore after it got into the net while they were fishing near Tongjiang of east Heilongjiang Province.

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The money he received from the local fishery release station in Fuyuan City was twice his salary, Ma was quoted as saying.

Last year, a giant sturgeon was also fished out from the same region. Weighing 450 kilos, the fishermen sold it for over $61,000. It was estimated to be about 100 to 200 years old.

According to Conservation Institute, Kaluga Sturgeon, also known as the river Beluga, is believed to be the world's largest freshwater fish.

The fish can reach over 15 feet long and weigh over 2,500 pounds. They can swim freely between salt and fresh water.

The largest recorded beluga sturgeon weight over 7,000 pounds and was almost 20 feet long.

Beluga sturgeon are prized for their eggs and their delicate skin.

'Humans consider their eggs a delicacy and have overfished these massive monster-sized fish to get them, leaving the beluga sturgeon endangered with little chance of survival,' the Conservation Institute stated in its website.

In a bid to reverse the species' endangered status, regulators have banned beluga sturgeon caviar in the United States.